Maintaining correct air pressure in a tire is one of the most important factors in maintaining tire performance, safety and service life. A careful driver will have the air pressure checked regularly with a hand held air pressure gauge pushed momentarily onto the tire valve stem. Unfortunately, it is not uncommon to forget to check the tire pressure and the pressure can easily vary from the optimum range because of temperature change or slow leakage. An underinflated tire will generate far more friction than a properly inflated tire, which at a minimum reduces the fuel efficiency of the vehicle. Underinflation also can lead to such severe heat buildup in the tire that the tire itself is destroyed.
A need exists to develop an improved, easily used technique for monitoring tire air pressure. Many attempts have been made to do this, including U.S. Pat. No. 3,719,159 to Davis issued Mar. 6, 1973, U.S. Pat. No. 3,977,355 to Lorenz et al. issued Aug. 31, 1976 and U.S. Pat. No. 4,476,803 to Malec issued Oct. 16, 1984. However, these prior concepts have not fulfilled this need.